NIFI-9970 Restructured Pull Request Template
NIFI-9970 Restructured Pull Request Template

- Added Summary, Tracking, and Verification section headings
- Reworded checklist to declarative statements instead of questions
- Added JDK 17 to list of build platforms

Signed-off-by: Pierre Villard <pierre.villard.fr@gmail.com>

This closes #6002.

jfrazee/nifi,pvillard31/nifi,pvillard31/nifi,jfrazee/nifi,pvillard31/nifi,jfrazee/nifi,pvillard31/nifi,pvillard31/nifi,jfrazee/nifi,pvillard31/nifi,jfrazee/nifi,pvillard31/nifi,jfrazee/nifi,jfrazee/nifi,pvillard31/nifi,jfrazee/nifi